In the immediate aftermath of the Boston Marathon bombing, federal, state and local law enforcement officials coalesced with an effectiveness — and with a swiftness — that took a lot of people by surprise. Perhaps no two people more so than the Brothers Tsarnaev.

Just stop and think how quickly this all unraveled for the alleged bombers: Four days after the backpack bombs exploded near the finish line of the country’s oldest race, killing three and wounding hundreds, 26-year-old Tamerlan was shot full of holes, and Dzhokhar, 19, who is said to have frantically eluded capture by driving over the body of his dying brother, was found bloodied and exhausted, cowering for cover in a boat in a neighbor’s yard.

These two didn’t know what hit them.

Spontaneity reveals a lot about people. As police evacuated the scene of the showdown in Watertown, Mass., late Friday evening, residents who had just endured a full day under martial-law lockdown took to the streets. Not to gawk but to applaud. Parents held children on their shoulders so they could see these heroes, the men and women in uniform who brought this ordeal to its definitive and righteous end. It was something out of World War II, when allied troops would liberate a village in France or Italy and the locals would gather and cheer — and if not chant “U-S-A, U-S-A” as they did in Watertown, at least wave an American flag or two.

What always resonates with people, whether they’re here or there and whether it’s now or more than a half century ago, is the forceful triumph of good over evil. On a glorious afternoon in Boston, as the civic holiday Patriot’s Day was at its zenith — the Red Sox had won in their last at-bat and runners were crossing the finish line at Copley Square — the flesh and bones of innocent people were shredded by incendiary devices made from pressure cookers and nails. And the alleged bombers did so without even the slightest breeze of provocation. What was their beef? That Chechnya is being oppressed by whom? Russia? That Tamerlan didn’t have any American friends? That Dzhokhar got the new girl at Supercuts? It’s as pointless as it is tragic.

But this is why we feel relieved today, even as we mourn four deaths — three taken by the explosions and the fourth, that of the MIT police officer, taken in the line of duty. We feel relieved because the good guys won, and they won decisively. They terrorized the terrorists, making them run for their lives like a couple of pathetic outlaws. And the justice they wrought upon them was immediate and — as it was for one and will be for the other — eternal.

Roger Snow is the chief product officer of SHFL entertainment. He was born and raised in Boston.